The Mugwandi school head said: “Pupils, particularly the girls, are collapsing in class and in the compound.”

Mr Njenga said the children went into convulsions once attacked.

“What is happening here is shocking and everybody is extremely worried,” he said. Equally perplexed are parents and teachers at the school with 500 pupils. Prayers are being held at the institution to exorcise the “evil spirits”.

The strange goings-on started last term and became worse this term, with the “invasions” occurring every three days, Mr Njenga said.

Doctors have said that the children could be suffering from mental disorders but parents dispute this.

Flying birds

Mr Njenga said a local Catholic priest recently visited the school and conducted a cleansing ceremony. “I believe in the power of prayer and things will soon be fine,” he said.

Pupils said they feel dizzy and then fall on the ground. They said they see flying birds and umbrellas in their classrooms and also in the compound.

A parent, Mr Gerald Karimi, said his Standard Four daughter is among the victims.

“When my daughter is at home, she behaves normally but when she goes back to school she starts behaving strangely,” said the 54-year-old man.